A prosthesis knockout tool is shown in German Patent Application DE 42 20 970 A1. The tool head is curved in order to compensate for an angling of the prosthesis shaft relative to a center axis of the prosthesis, so that the joint prosthesis that has been inserted into the bone can be knocked out in the extension of the center axis of the prosthesis. The angle of curvature of the tool head is therefore essentially equivalent to the angling of the prosthesis shaft relative to the center axis of the prosthesis. Misalignment between the knockout force vector and the center axis of the prosthesis causes splintering of the bone surrounding the joint prosthesis, which is undesired.
The knockout tool known from German Patent Application DE 42 20 970 A1 has a tongue that is formed on a lever arm supported outside the tool head and is intended for engagement with a recess formed in the prosthesis shaft, in order to lock the prosthesis to the tool head. Hence that tool requires a large amount of space.
The prosthesis shafts of conventional joint prostheses are not standardized and have different diameters. However, previously known knockout tools do not adequately take such different prosthesis shaft diameters into account, and adaptation to various diameters is complicated. When such knockout tools are used with such prosthesis shafts of small diameter, the prosthesis shaft is not always locked in the tool head without play and form-fittingly.
It must also be taken into account that the pivot lever, supported outside the tool head in the previously known knockout tool, increases the space required by the tool considerably. Yet there is only limited space available for the knockout tool at the site of the operation.